Stalk rot infection reduces the efficiency of carbohydrate transport from the stalk up to the ears during grainfill, which reduces crop yield. A corn plant will die altogether if infection advances to the point that the pith pulls away from the outer rind of the stalk, which can eventually result in a stalk consisting of little more than a hollow tube that is no longer able transport water and nutrients to the rest of the plant. Furthermore, a stalk weakened by infection is more likely to collapse at one or more points along its length (lodging), which typically results in a plant that yields no harvestable grain. Stalk rots typically reduce yields up to 5% in almost any field where corn is cultivated. In years with particularly bad infection rates, yield losses reach 10-20%, and in some locations when infection is particularly acute, 100% yield loss can occur.
One of the most common forms of stalk rot is Fusarium stalk rot, caused by several species of fungi, including Fusarium verticilliodes e J. Sheld. (sexual stage: G. moniliformis Sawada) Ito in Ito & Kimura, formerly Fusarium moniliforme, telemorph Gibberella fujikoroi, F. proliferatum (T. Matsushima) Nirenberg (sexual stage: G. proliferatum), and F. subglutinans (sexual stage: G. subglutinans). FSR infection is characterized by rotting roots, crown, and lower internodes that begins shortly after pollination and progresses as the plant matures. Eventually the pith will disintegrate resulting in weak, spongy stalks that are prone to lodging.
Due to the lack of fungicides and or other chemical controls for FSR, growers are faced with limited options for managing the disease. Since the most effective approach is to select hybrids that are intrinsically resistant, what is needed are methods of identifying genetic sources of FSR resistance and more effective methods of introgressing those genetic elements into commercial lines to provide new hybrids with improved genetic resistance to FSR infection.